Negative thermal diffusivity enhancement in semiconductor nanofluids

摘要

Colloidal suspensions of semiconductor InP@ZnS nanoparticles were prepared using single-step procedure without precursor injection. Thermal properties of toluene containing InP@ZnS semiconductor with different sizes (3.1, 4.2, and 4.6 nm) were measured by mode mismatched dualbeam thermal lens technique. This was done in order to measure the effect of the presence of semiconductor nanoparticles and size on the nanofluids thermal diffusivity. The characteristic time constant of the transient thermal lens was estimated by fitting the experimental data to the theoretical expression for transient thermal lens. The thermal diffusivity of the nanofluids (toluene, containing InP@ZnS semiconductor nanoparticles) it seems to be strongly dependent on the presence of semiconductor nanoparticles and particles size. For the case of nanofluids consisting of InP@ZnS nanoparticles dispersed in toluene, it was observed a decrease in the thermal diffusivity. Such behavior differs from other nanofluids, in the sense that they had shown positive thermal diffusivity enhancement. The minimum diffusivity was achieved for the nanoparticles with lowest size. Plausible explanation for such nanofluids low thermal diffusivity with semiconductor nanoparticles is given. UV-Vis spectroscopy, TEM and high-resolution electron microscopy (HRTEM), and energy dispersive spectroscopy (EDS) techniques were used to characterize the InP@ZnS nanoparticles.